R/isClosed.r

In ODB: Open Document Databases (.odb) Management

### Copyright (C) 2012 Sylvain Mareschal <maressyl@gmail.com>
### 
### This program is free software: you can redistribute it and/or modify
### it under the terms of the GNU General Public License as published by
### the Free Software Foundation, either version 3 of the License, or
### (at your option) any later version.
### 
### This program is distributed in the hope that it will be useful,
### but WITHOUT ANY WARRANTY; without even the implied warranty of
### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
### GNU General Public License for more details.
### 
### You should have received a copy of the GNU General Public License
### along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Check if a DBI or odb connection is closed
isClosed = function(
		connection
		)
	{
	# Connection check
	if (!inherits(connection, "DBIConnection")) {
		stop("'connection' must inherit from 'DBIConnection', or be an 'ODB' connection")
	}
	
	# dbSendUpdate() returns TRUE on success (uses to return NULL)
	isOpen <- try(dbSendUpdate(connection, ""), silent=TRUE)
	if(is.null(isOpen)) isOpen <- TRUE
	if(is(isOpen, "try-error")) {
		cnd <- attr(isOpen, "condition")
		if(conditionMessage(cnd) == "java.sql.SQLException: Connection is closed") {
			# Connection is actually closed
			isOpen <- FALSE
		} else {
			# Other error to let through
			stop(cnd)
		}		
	}
	
	return(!isOpen)
}